The present invention relates generally to solder-less printed circuit board edge connectors, and, more particularly, to a solder-less printed circuit board edge connector having a common ground contact for a plurality of transmission lines.
A transmission line, formed as a coaxial cable or on a printed circuit board, has an unbalanced construction and an impedance characteristic of the transmission line, as is well known in the art. The unbalanced construction means that the electrical charge density per unit area on the outer conductor of the coaxial cable is less than the electrical charge density per unit area on the inner conductor of the coaxial cable. The impedance (Z) is defined as the square root of the result of inductance (L) of the transmission line divided by the capacitance (C) of the transmission line.
A connector that connects one transmission line to another transmission line needs to efficiently maintain the unbalanced construction and the impedance characteristics of the transmission line across the connector and at the interface of the connector to each transmission line. Inefficiency in the connector itself or at the interface of the connector to either transmission line causes an insertion loss or degradation of the construction and impedance characteristics of the transmission line resulting in a corresponding loss or degradation of the signal carried by the transmission line. Insertion loss may be due to reflection of the signal, resistance in the transmission line, inappropriate leakage of the signal, or inappropriate dielectric properties in the transmission line, as are all well known in the art. In turn, such an insertion loss or degradation of the signal carried by the transmission line reduces the operating performance of the system using the signal.
Two-piece coaxial cable connectors having a male connector piece connected to a coaxial cable and a female connector piece connected to a printed circuit board are well known in the art. Typically, the female connector piece is soldered to the printed circuit board near an edge of the printed circuit board. When several or many two-piece coaxial cable connectors are needed in a local area, a bridge connector, sometimes called a xe2x80x9cgo betweenxe2x80x9d connector or a block connector, may be used to couple all of the coaxial cables to the multiple female connector pieces at the same time, as is well known in the art. Problems associated with the bridge connector include: misalignment between multiple male connector pieces mounted on the bridge connector and the multiple female connector pieces mounted on the printed circuit board, excessive insertion force required to mate the multiple male connector pieces mounted on the bridge connector and the multiple female connector pieces mounted on the printed circuit board, excessive cost and weight associated with the two-piece connector, decreased reliability and electrical performance associated with the two-piece connector, and potential replacement or rework problems associated with the multiple female connector pieces soldered to the printed circuit board.
Solder-less printed circuit board edge connectors are typically used for interconnecting printed circuit boards or for connecting a plurality of wires to a printed circuit board. Signal contacts and ground contacts on the printed circuit board electrically couple to signal contacts and ground contacts on the edge connector when the edge of the printed circuit board is inserted into the edge connector. Preferably, the edge connector is secured to a nearby case or a header mounted on the edge of the printed circuit board.
A coaxial cable connector employing a solder-less printed circuit board edge connector needs to translate the construction and impedance characteristics of a transmission line, formed as a coaxial cable, to a corresponding construction and impedance characteristics of a transmission line, formed on a planar printed circuit board.
Hence, a coaxial cable connector employing an edge connector needs to provide a coaxial-to-planar translation (or planar-to-coaxial translation) of the construction and impedance characteristics of a transmission line.
Generally, connectors also need to be designed to minimize parts count, decrease cost, increase reliability, increase the speed of the assembly of the connector, decrease cost, and the like. The following patents describe various types of connectors known in the art and a deficiency associated with each of the described connectors.
U.S. Pat. No. 4,605,269, issued Aug. 12, 1986 to AMP Inc., discloses a coaxial connector soldered to a printed circuit board for accepting multiple coaxial cables.
However, this patent does not disclose eliminating the coaxial connector.
U.S. Pat. No. 4,801, 269, issued Jan. 31, 1989 to The Regents of the University of California, discloses a coaxial cable connector for use with a printed circuit board edge connector to connect a single coaxial cable to a micro-strip line at the edge of a printed circuit board. However, this patent does not disclose: how to match an impedance between an edge connector and a micro-strip line, a ground contact integrally formed with a connector housing, a mechanism integrally formed with the connector for retaining the coaxial connector directly to a printed circuit board, a common ground contact electrically coupled to a ground potential of multiple transmission lines, or a signal contact having an spring finger integrally formed with a receptacle adapted to receive a center conductor of a coaxial cable, each for use with a solder-less printed circuit board edge connector.
U.S. Pat. No. 5,100,344, issued Mar. 31, 1992 to AMP Inc., discloses a BNC connector soldered to a printed circuit board, wherein the BNC connector is adapted to mate to a receiving connector attached to a coaxial cable. However, this patent does not disclose eliminating the BNC connector soldered to the printed circuit board.
U.S. Pat. No. 5,123,863, issued Jun. 23, 1992 to TRW Inc., discloses a solderless housing interconnect for a miniature semi-rigid coaxial cable, wherein the coaxial cable extends perpendicular to and through a hole in a printed circuit board to contact a ribbon cable coupled to a micro-strip. However, this patent does not disclose a connector for attaching a coaxial cable to an edge of a printed circuit board.
U.S. Pat. No. 5,169,343, issued Dec. 8, 1992 to E. I. Du Pont de Nemours and Company, discloses a connector soldered to a printed circuit board and adapted to receive multiple coaxial cables. However, this patent does not disclose eliminating the connector soldered to the printed circuit board.
U.S. Pat. No. 5,176,538, issued Jan. 5, 1993 to W. L. Gore and Associates, Inc., discloses a connector for multiple coaxial cables having a plurality of signal contacts and having a ground shield integrally formed with spring finger ground contacts, wherein the connector connects to a mating connector soldered to a printed circuit board. However, this patent does not disclose that the connector and spring fingers mate directly to a micro-strip at an edge of a printed circuit board.
U.S. Pat. No. 5,190,474, issued Mar. 2, 1993 to Radiall, Rosny-sous-Bois, France, discloses a first connector attached to a coaxial cable and a second connector soldered to a printed circuit board, wherein the first connector and the second connector are electrically and mechanically designed for coupling and decoupling. However, this patent does not disclose eliminating the second connector soldered to the printed circuit board.
U.S. Pat. No. 5,334,050, issued Aug. 2, 1994 to Derek Andrews, discloses a surface mounted connector soldered to a printed circuit board and adapted to receive multiple individual coaxial cables. However, this patent does not disclose eliminating the surface mounted connector soldered to the printed circuit board.
U.S. Pat. No. 5,478,258, issued Dec. 26, 1995 to Tsan-Chi Wang, discloses a BNC connector soldered to a printed circuit board, wherein the BNC connector is adapted to mate to a receiving connector attached to a coaxial cable. However, this patent does not disclose eliminating the BNC connector soldered to the printed circuit board.
U.S. Pat. No. 5,588,851, issued Dec. 31, 1996 to Framatome Connectors International, discloses a connector for connecting multiple coaxial cables with contact pins to a printed circuit board. The female ground contact members are formed out of and unitary with a ground plate. However, this patent does not disclose that the connector or the ground contact members attaches the coaxial cable to a micro-strip at an edge of the printed circuit board.
U.S. Pat. No. 5, 613,880, issued Mar. 25, 1997 to Tsan-Chi Wang, discloses a dual plug BNC connector soldered to a printed circuit board, wherein the BNC connector is adapted to mate to a receiving connector attached to a coaxial cable. However, this patent does not disclose eliminating the BNC connector soldered to the printed circuit board.
U.S. Pat. No. 6,007,347, issued Dec. 28, 1999 to Tektronix, Inc., discloses a BNC connector having a coaxial cable with insulation stripped back and disposed in a slot in a printed circuit board such that the stripped back inner conductor rests on and is soldered to a conductive pad on the printed circuit board. This patent also discloses selecting a distance between the sides of the conductive pad and the near edges of elongated holes in the printed circuit board to provide a predetermined transition impedance. However, this patent does not disclose eliminating the BNC connector mounted on the printed circuit board. Further, this patent does not disclose modifying the BNC connector to provide a predetermined impedance match.
U.S. Pat. No. 6,045,402, issued April 4, 2000 to Siemens, discloses a connector surface mounted with solder to a printed circuit board and adapted to receive multiple coaxial cables. FIG. 5 shows an integral lead/tubular lead-through, wherein the tube end accepts the inner conductor of the coaxial cable and the lead end is surface mounted with solder to the printed circuit board. However, this patent does not disclose eliminating the connector surface mounted with solder to the printed circuit board. Further, this patent does not disclose that an integral spring finger/tubular lead, wherein the spring finger provides a sliding connection to a micro-strip at an edge of a printed circuit board.
U.S. Pat. No. 6,065,976, issued May 23, 2000 to Tsan-Chi Wang, discloses a T-shaped BNC connector having slots for accepting and being soldered to a printed circuit board, wherein the BNC connector is adapted to mate to a receiving connector attached to a coaxial cable. However, this patent does not disclose eliminating the BNC connector soldered to the printed circuit board.
U.S. Pat. No. 6,149,461, issued Nov. 21, 2000 to ProComm, Inc., discloses a solder-less coaxial cable termination-mounting device, wherein a first portion of the device is soldered to a printed circuit board and other portions are assembled to retain the inner conductor, the outer conductor and the insulation of the coaxial cable. However, this patent does not disclose eliminating the first portion of the device that is soldered to the printed circuit board as well as the other portions of the assembly.
The foregoing patents do not teach or suggest, alone or in combination, a solder- less printed circuit board edge connector having a common ground contact for a plurality of transmission lines. Accordingly, there is a need for a solder-less printed circuit board edge connector having a common ground contact for a plurality of transmission lines to advantageously minimize parts count, increase reliability, minimize rework or replacement, decrease cost, decrease labor for the assembly of the connector, and the like.